Lower Respiratory (Microbiology)

Question 1

72

A 10 year old child with cystic fibrosis presents with cough and shortness of breath. Her sputum Gram stain is seen in the image.
Based on the Gram stain the best medium and incubation condition to optimize recovery of the organism seen is:

A) MacConkey agar incubated in CO2
B) Tinsdale agar incubated in ambient air
C) chocolate agar incubated in CO2
D) CNA agar icubated in ambient air

Answer 1

C) chocolate agar incubated in CO2

Question 2

A sputum culture from an alcoholic seen in the ER grows gray, mucoid, stringy colonies on sheep blood agar. The isolate grows readily on MacConkey agar and forms mucoid, dark pink colonies. The colonies yield the following test results:

ONPG: pos
indole: neg
glucose: pos
oxidase: neg
citrate: pos
VP: pos

The organism is most likely:
A) Edwardsiella tarda
B) Klebsiella pneumoniae
C) Escherichia coli
D) Proteus vulgaris

Answer 2

B) Klebsiella pneumoniae

Question 3

A patient with a nosocomial pneumonia has a sputum Gram stain that shows many neutrophils and numerous small gram-negative coccobacilli. The organism grew in 24 hrs as a mucoid, hemolytic colony on blood agar and a colorless colony on a MacConkey agar. The organism had the following characteristics:

oxidase: neg
catalase: pos
nitrate: neg
ONPG: neg
ornithine decarboxylase: neg
lysine decarboxylase: neg

The organism is:
A) Stenotrophomonas maltoophilia
B) Alcaligenes faecalis
C) Moraxella lacunata
D) Acinetobacter baumannii

Answer 3

D) Acinetobacter baumannii

Question 4

Serum samples collected from a patient with pneumonia demonstrates a rising antibody titer to Legionella. A bronchoalveolar lavage (BAL) specimen from this patient had a positive antigen test for Legionella but no organisms were recovered on buffered charcoal yeast extract medium after 2 days of incubation. The best explanation is that the:

A) antibody titer represents an earlier infection
B) positive antigen test is a false-positive
C) specimen was cultured on the wrong media
D) culture was not incubated long enough

Answer 4

D) culture was not incubated long enough

Question 5

A 17 year old female with cystic fibrosis is diagnosed with pneumonia. A sputum sample grew gram-negative bacilli with yellow, smooth colonies that have the following biochemical reactions:

oxidase: pos
TSI: alk/alk
glucose: oxidized
fluorescence: neg
lysine decarboxylase: pos

The most likely organism is:

A) Burkholderia cepacia
B) Klebsiella pneumoniae
C) Shewanella putrefaciens
D) Stenotrophomonas maltophilia

Answer 5

A) Burkholderia cepacia

Question 6

A college student who recently studied a semester abroad in Southeast Asia is admitted to the hospital with a diagnosis of “glanders-like” infection (melioidosis). A sputum specimen grows small, gram negative bacili that are positive for oxidase, reduce nitrate to gas, and oxidize glucose, lactose, and mannitol. What is the most likely organism?

A) Stenotrophomans maltophilia
B) Burkholderia pseudomallei
C) Pseudomonas aeruginosa
D) Acinetobacter baumannii

Answer 6

B) Burkholderia pseudomallei

Question 7

An organism previously thought to be non-pathogenic, Moraxella catarrhalis, is now known to be associated with opportunistic respiratory infecitn and nosocomial transmission.

A) beta-lactamase negative
B) butyrate esterase positive
C) gram negative bacilli
D) oxidase negative

Answer 7

B) butyrate esterase positive

Question 8

An organism recovered from a sputum has the following characteristics:

culture: growth at 6 days on buffered charcoal yeast extract (BCYE) agar, incubated under aerobic conditions with CO2 at 35 degrees C
Gram stain: delicate branching gram-positive bacili
modified acid-fast stain: branching, filamentous, “partially”, acid-fast bacterium

These results are consistent with which of the following genera?

A) Nocardia
B) Mycobacterium
C) Actinomyces
D) Streptomyces

Answer 8

A) Nocardia

Question 9

The gram stain of drainage from a pulmonary sinus tract shows many WBCs and 3+ branching gram-positive bacilli. Colonies grow only on anaerobic media after 3 days incubation. They are yellow-tan and have a molar tooth appearance. The most likely genus is:

A) Actinomyces
B) Bacteroides
C) Fusobacterium
D) Nocardia

Answer 9

A) Actinomyces

Question 10

A 1-2 mm translucent, nonpigmented colony, isolated from an anaerobic culture of a lung abscess after 72 hrs, was found to fluoresce brick-red under ultraviolet light. A Gram stain of the organism revealed coccobacili that had the following characteristics:

growth in bile: inhibited
vancomycin: resistant
kanamycin: resistant
colistin: susceptible
catalase: neg
esculin hydrolysis: neg
indole: neg

The identification of this isolate is: